1. Technical Field
The invention relates to a torque wrench, comprising
(a) an elongated outer housing, PA1 (b) an inner part extending in the outer housing and pivotably connected thereto in the proximity of a first end of the torque wrench, PA1 (c) a tool arranged at the first end, PA1 (d) a handle portion arranged at the second end of the torque wrench, and PA1 (e) a spring loaded toggle lever mechanism acting between the handle portion and the element carrying the tool, which toggle lever mechanism releases when a torque exerted on the tool through the handle portion, the toggle lever mechanism and said element is exceeded, and which permits a pivotal movement between outer housing and inner part. PA1 (f) the tool is attached to the outer housing, and PA1 (g) the inner part is rigidly attached to the handle portion.
2. Background Art
Such a torque wrench is known, for example, from U.S. Pat. No. 4,655,104. In this torque wrench the inner part is a solid body, which is mounted in the outer housing at its first end and which carries a tool at its end extending out of the outer housing. A link is pivoted with one of its ends at the end of the inner part on the handle side. A pin is located at the other end of the link, a spring acting longitudinally of the outer housing pressing on this pin. The inner part and the spring loaded link form a toggle lever mechanism, which releases, overcoming the bias of the spring, when a predetermined torque has been exceeded, and which permits snapping movement of the inner part relative to the outer housing, providing an audible and tactile signal.
Similar releasing torque wrenches are shown in U.S. Pat. No. 3,202,021, British patent No. 966,947 and German patent document No. 25 53 326. Therein the toggle lever mechanism consists of a spring loaded lever supported with a roller on the inner wall of the outer housing and a link connecting this lever with the inner part.
In another known torque wrench the toggle lever mechanism comprises a lever, which is pivotably mounted in the outer housing and the handle portion integral therewith. This lever presses with one end on the end of the inner part adjacent to the handle. The other end of the lever is connected through a link to a spring loaded slider longitudinally movable in the outer housing.
In the known torque wrenches the torque is transmitted through the inner part. Thus, this inner part has to be very stable. Because the inner part is arranged within the outer housing, this stability is achieved only by a solid construction of the inner part, usually as forged part. This, in turn, results in the torque wrench becoming rather heavy.
A further disadvantage of the known torque wrenches of the type described above consists in that the point of rotation of the screw, about which the user exerts the torque on the screw, is substantially different from the pivot point of the inner part relative to the outer housing, which serves as "functional point of rotation". This results in the releasing point being very much dependent on the point of attack at the handle portion.
German patent No. 679,042 discloses a wrench having limited force transmission. In this wrench, two elongated housing portions cut-off along oblique planes, namely a tool-side housing portion and a handle-side housing portion, are interconnected by a pivot axle. A bending spring, on one side thereof, is supported both on the pivot axle and on a transverse axle provided in the handle-side housing portion. On the opposite side, an adjusting screw engages the bending spring between these two axles. A desired bias of the bending spring can be set by means of the adjusting screw. A handle is attached to the end of the bending spring extending from the handle-side housing portion. Furthermore a lug is provided on the bending spring and extends over a locking pawl and retains this pawl in its operative position. The locking pawl, in its operative position, extends over a stop provided on the tool-side housing portion and keeps the housing portions in an extended mutual position. The tool-side housing portion carries a tool.
When the torque acting on the bending spring exceeds the bias set by the adjusting screw, the bending spring yields. The lug then releases the blocking pawl. The blocking pawl, in turn, releases the stop, whereby the two housing portions will be deflected.